I am actually surprised at the speed with which the Mexican govt. has responded to the attacks. It sounds like a good start. Monitoring the swimming and surfing areas is probably a prudent idea in the near term. Tiger Sharks often patrol a certain area for a period of time then leave if their food source dwindles. I suspect that the sharks were foraging in the area where the swimmers got hit.
I know that one of their prime food sources, turtles, are in that area. Perhaps turtles had gathered off the beaches in preparation for laying their eggs in the sands. Hawaii has a similar situation. They have tried catching and killing the offending shark after an attack but that doesn’t really work because the offending shark has usually moved out of the area after and attack and what they usually catch are other sharks that are residents of the local reefs.